Context

包路径: github.com/caicloud/nirvana/service

在 Nirvana 中，Context 用于传递请求的上下文。Context 中包含 HTTP 的 Request 和 ResponseWriter。可是使用 service 包的 HTTPContextFrom() 方法获得 HTTP Context。HTTP Context 相关接口如下：

  1. // ValueContainer contains values from a request.
  2. type ValueContainer interface {
  3.     // Path returns path value by key.
  4.     Path(key string) (string, bool)
  5.     // Query returns value from query string.
  6.     Query(key string) ([]string, bool)
  7.     // Header returns value by header key.
  8.     Header(key string) ([]string, bool)
  9.     // Form returns value from request. It is valid when
  10.     // http "Content-Type" is "application/x-www-form-urlencoded"
  11.     // or "multipart/form-data".
  12.     Form(key string) ([]string, bool)
  13.     // File returns a file reader when "Content-Type" is "multipart/form-data".
  14.     File(key string) (multipart.File, bool)
  15.     // Body returns a reader to read data from request body.
  16.     // The reader only can read once.
  17.     Body() (reader io.ReadCloser, contentType string, ok bool)
  18. }
  20. // ResponseWriter extends http.ResponseWriter.
  21. type ResponseWriter interface {
  22.     http.ResponseWriter
  23.     // HeaderWritable can check whether WriteHeader() has
  24.     // been called. If the method returns false, you should
  25.     // not recall WriteHeader().
  26.     HeaderWritable() bool
  27.     // StatusCode returns status code.
  28.     StatusCode() int
  29.     // ContentLength returns the length of written content.
  30.     ContentLength() int
  31. }
  33. // HTTPContext describes an http context.
  34. type HTTPContext interface {
  35.     Request() *http.Request
  36.     ResponseWriter() ResponseWriter
  37.     ValueContainer() ValueContainer
  38.     RoutePath() string
  39. }

Nirvana 框架会为每个请求构建这样的 HTTPContext。如有必要，可以通过这些接口拿到与请求相关的所有数据。

在一个请求路由匹配成功后，Nirvana 会把对应的 HTTPContext 传递给中间件，然后由中间件调用链继续传递。最终经由 ContextPrefab 传递给业务函数。

中间件不应该修改 HTTPContext，除非您明确知道如何修改。